1. Field of the Invention
The present invention generally relates to the field of semiconductor devices, and more particularly, to Hall-effect sensors.
2. Related Art
Typically, Hall-effect sensors (hereafter called Hall sensors) are used to measure (1) static, transient or dynamic magnetic fields, (2) a current by measuring the magnetic field produced by the current, (3) a current passing through the sensor, or (4) material properties of the semiconductor in which the sensor is formed. Hall sensors are employed in a wide variety of applications including, for example, automotive, medical, power electronics, computer sensors, transducers, material characterization and power meters.
The well known Hall-effect is summarized in FIG. 1, which illustrates a circuit diagram of an N-type semiconductor material configured to produce the Hall-effect. A current, I.sub.DC, is forced through the material by an external voltage, V.sub.DC. An external magnetic field, B, applied perpendicular to the current I.sub.DC generates a "Hall voltage", V.sub.H. The Hall voltage is produced as a result of the Lorentz force on a charge, e, moving through a perpendicular magnetic field with a velocity, v. The following equation shows the relationship of I.sub.DC to V.sub.H, and V.sub.DC to V.sub.H in terms of the sensor size ratio, w/l (width, w, to length, l,): ##EQU1##
The Hall-effect can be obtained using both N-type and P-type semiconducting material. However, N-type semiconducting material is selected for most sensors because the mobility, .mu. (average velocity/electric field) is higher for electrons. For discussion purposes, N-type material will be assumed.
Further, background material concerning semiconductor solid-state physics may be found in a number of references including two books by S.M. Sze, titled: Physics of Semiconductor Devices, John Wiley and Sons, Inc., New York (1981), and Semiconductor Devices, Physics and Technology, John Wiley and Sons, Inc., New York (1985), both of which are incorporated herein by reference.